T245 Ecosystem Engineering through Earth History

Friday, 30 October 2020
10:00 AM - 2:00 PM
Meeting Rooms

EARLY PALEOZOIC BIOTURBATION AND FEEDBACKS ON PHOSPHORUS CYCLING

Paper number: T245-6
Program: Technical Sessions
Time: 11:15 AM – 11:30 AM

Authors

  • Lidya Tarhan Presenting Author
    Yale University, Dept. Earth and Planetary Sciences, New Haven, CT

Abstract

Bioturbation—sediment mixing and ventilation by burrowing animals—provides one of the most prominent examples of how animals shape their surroundings. A critical but longstanding question is when and how in Earth’s history bioturbators began to similarly influence marine biogeochemistry. Recent work has proposed that even though the development of well-mixed sediments was a protracted process, the early rise of bioturbators led to a decrease in marine phosphate levels, global productivity crises and ultimately deoxygenation events in the early Cambrian oceans. However, a paucity of biogeochemical models with both realistic representation of bioturbation and full, mechanistic parameterization of benthic phosphorus cycling has hampered efforts to test these hypotheses. In order to address these issues, I used a modified version of the SedChem diagenetic model (cf. Zhao et al., 2020) to explore, in a quantitative and process-based manner, the relationship between bioturbation and global phosphorus cycling. In contrast to previous modeling studies, I find that bioturbation does not uniformly or unidirectionally mediate increased phosphorus burial. Enhanced biodiffusion of sedimentary particles can mediate enhanced phosphorus burial. In contrast, bioirrigation—nonlocal advectional transport of solutes via open burrows—facilitates enhanced phosphorus recycling, stimulating rather than stymying productivity. Given evidence from the geologic record that bioirrigation rather than biodiffusion was predominant during the early Paleozoic ramping up of bioturbation, the emergence of bioturbation is unlikely to have driven deoxygenation events but may have enhanced the sensitivity of marine biogeochemical systems to environmental perturbation.

Geological Society of America Abstracts with Programs. Vol. 52, No. 6

doi: 10.1130/abs/2020AM-359598

© Copyright 2020 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.